We thank the members of the laboratories at Ube National

We thank the members of the laboratories at Ube National College of Technology for their help with field and laboratory work. This study was partially supported by a grant from the Environment Research and Technology Development Fund of the Ministry of the Environment, Japan (F1102).
1. Introduction
After the disastrous flood in southern Poland in 1997, the central and regional authorities implemented a modernisation programme of hydrotechnical systems alongside the Oder River (Oder 2006 programme). The rebuilding of “hydrotechnical CPI-169 Opole” was a part of this project which main goal was to increase the water capacity of the river valley during the inundations. As it was enumerated in the project, the regional authorities build new water embankments and a new bypass channel. As a result two oxbow lakes have to be eliminated. During the environmental impact assessment procedure the creation of three artificial ox-bows has been imposed on investor as a compensation measure.
The main goal of this study is to assess the vegetation changes and population dynamics of target species in these artificial oxbows. After habitat recreation, we started observations of the secondary succession to determine the directions of vegetation changes and predict the longevity of that kind of artificial reservoirs. At the beginning of our study it was hypothesised that the secondary succession would start shortly after recreation of oxbow lakes. The fast colonisation by different therophytes and anthropophytes as well as expansive native species and alien invasive species would happen on the lake banks. We expected also that spreading of expansive native plants like P. australis and increasing participation of alien invasive plants (common in the Oder valley) would occur after about 5 years further. However, we were not sure what the succession rate and the dynamics of distinct species populations would be.